Spring boot 如何使用rest模板从api调用返回的对象中检索对象属性

我使用SpringREST模板作为rest客户机进行了api调用。当生成api的方法返回字符串时，postman能够看到对象及其值的关联对象属性。但是，当我将返回类型更改为对返回的api对象建模的对象时，会得到所有空值。我做错什么了吗

@GetMapping(value="/verbvn/{xbvn}")
public Participant verBVN(@PathVariable String xbvn) {
    System.out.println("bvn is "+xbvn);
    HttpHeaders headers = new HttpHeaders();
      headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
      headers.setBearerAuth("sk_live_32a7ffd9cc47f");
      HttpEntity <String> entity = new HttpEntity<String>(headers);


      Participant r= restTemplate.exchange("https://api.stck.co/bnk/resolve_bvn/"+xbvn, HttpMethod.GET, entity, new ParameterizedTypeReference<Participant>() {}).getBody();
      System.out.println("the participant firstname is "+r.getFirstName());

      return r;

}

public class Participant {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column
private Long id;

@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name="id",referencedColumnName="id")
private Data data;

public Participant() {

}

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public Data getData() {
    return data;
}

public void setData(Data data) {
    this.data = data;
}

---

显示参与者类，该类中是否有设置者？@Deadpool我已编辑我的初始帖子以反映所涉及的类。显示参与者类，该类中是否有设置者？@Deadpool我已编辑我的初始帖子以反映所涉及的类。

@Entity
@Table
@Async
@JsonIgnoreProperties(ignoreUnknown=true)
public class Data {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column
private Long id;
@Column
@JsonProperty(value="first_name")
private String firstName;
@Column
@JsonProperty(value="last_name")
private String lastName;
@Column
@JsonProperty(value="phone")
private String phoneNumber;
@Column
@JsonProperty(value="email")
private String email;


public Data() {}

public Long getId() {
    return id;
}
public void setId(Long id) {
    this.id = id;
}
public String getFirstName() {
    return firstName;
}
public void setFirstName(String firstName) {
    this.firstName = firstName;
}
public String getLastName() {
    return lastName;
}
public void setLastName(String lastName) {
    this.lastName = lastName;
}
public String getPhoneNumber() {
    return phoneNumber;
}
public void setPhoneNumber(String phoneNumber) {
    this.phoneNumber = phoneNumber;
}
public String getEmail() {
    return email;
}
public void setEmail(String email) {
    this.email = email;
}



}